Manufacture of ammonium phosphates



Aug. 18, 1936. H. A. CURTIS 2,051,029

MANUFACTURE OF AMMONIUM PHOSPHATES Filed May 21, 1954 i REACTIVE LJQUID15 :NIJ 1NER.TGA5

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ATTORNEY Patented Aug. 18, 1936 UNITED STATES MANUFACTURE OF AMMONIUMPHOSPHATES Harry A. Curtis, Knoxville. Tenn., asslgnor to TennesseeValley Authority, Wilson Dam, Alas a corporation of the United StatesApplication May :1, 1934, Serial No. mass 4 Claims. (01. za-io'n(Granted nnder the act of March a, less, as amended April :0, 1928; :10o. a. m)

This invention relates to an improved process of and apparatus forcausing a gas to react with a liquid under conditions such that theproper temperature for reaction is controlled to obtain a product ofuniform quality, particularly in connection with the manufacture ofammonium salts from ammonia and phosphoric acid. This application ismade under the act of April 30, 1928, and the invention hereindescribed, if m patented, may be manufactured and used by or for theGovernment for governmental purposes without the payment to me of anyroyalty thereon.

One of the objects of this invention is the control of the conditions ofreaction so that the resulting product may be the one selected from theseveral compounds capable of being made from a. given set of reactants.Another object of this invention is the providing for a means of con- 20tact for reactants so that substantially complete union is eflected,especially in the cases where one or both of the reactants are used incon-' centrated form. Other objects include the means for removal of aportion or all of the heat of reac- 25 tion and the means for theproduction of a dry granular of high quality.

Three ammonium phosphates may be made by combining ammonia andphosphoric acid, namely, 'mono-ammonimn phosphate, di-ammonium 30phosphate and tri-ammonium phosphate. Am-

monia and sulfuric acid will yield two ammonium sulfates, themono-ammonium sulfate known as ammonium bisuliate and the di-ammoniumsuliate' which is commonly called ammonium sul- 35 fate.

, I have found that, by spraying a reactive liquid into the top of atall reaction tower in which the temperature of the reaction zone iscontrolled and by distributing a mixture of reactive gas and 40 a secondgas, which is inert chemically under the conditions of operation, sothat the gas mixture will pass upward from near the bottom of thereaction tower, a solid product of reaction falls to the bottom of thetower. The flow of 45 the reactive liquid and the flow of the reactivegas are so regulated that the deliveries to the reaction tower are insubstantially stoichiometric proportions. The proportions of reactivegas and inert gas are so adjusted that the partial pres- 5 sure of thereactive gas is greater than the vapor pressureof the reactive gas forthe compound selected to be formed at the temperature of the reactionzone and less than the vapor pressure of the reactive gas for the nexthigher vapor pres- 55 sure compound of the series for the sametemperature of the reaction zone, where such a compound is known toexist. The vapor pressures of ammonia for one such series of compounds,the ammonium orthophosphates, included in the data presented in thepaper of Ross, Merz and Jacob on the Preparation and Properties ofAmmonium Phosphates, published in Industrial and Engineering Chemistry21, 288 (1929) March, are as follows:

I have also found that, in some instances, it is desirable to remove anyexcess of unreacted gas held by the reaction product by contacting thelatter with a gas, which is inert chemically under the conditions ofoperation, in a finishing tower and finally to remove the reactive gasfrom the inert gas by admitting the mixture to the bottom of thereaction tower. I A diagrammatic vertical section of one form ofapparatus for the embodiment of my process is shown in the accompanyingdrawing. The reactive liquid reservoir l, connects by valved line 2,through the top of the reaction tower 3, to a distributor S. The valvedreactive gas line 5, joins the valved inert gas line 6, and passesthrough the side of tower 3, near the bottom to distributor I. The motor8, through the speed reducer 9, drives the screw conveyor l0, whichcharges from the bottom of tower 3, and discharges on the distributor H,into the fiinishing tower l2. The second valved inert gas line i3, 40passes through the side of tower 12, near the bottom and joins thedistributor I l. The inert gas exits through valved line IS. The motorl6, through the speed reducer l'l, drives the screw conveyor I 8, whichcharges from the bottom of tower l2, and discharges into the valvedoutlet l9. One example of the operation of my process is given for themanufacture of mono-ammonium phosphate: phosphoric acid, containing 90%HaPO4, is admittedcontinuously and uniformly to the top of a reactiontower at a rate of flow of 98 parts by weight in a given time and 1'7parts by weight of gaseous ammonia admixed with air in volume ratios of25 to 735 are distributed from near the bottom of the reaction tower sothat the adjusted-to the minimum required for the sub-" stantiallycomplete removal of held by the reaction product. v

Another example of the functioning of my process is shown for themanufacture of diammonium phosphate: phosphoric acid, containex'cwsammonia ing HJPOi, is admitted at a rate of flow of 98 parts by weightand 34 parts by weight of ammonia admixed with air in volume ratios of 1to 9 are contacted at the same reaction zone temperature following thesame procedure as described in the foregoing example.

An additional example is given for the production of ammonium. sulfate:sulfm-ic acid, containing 60% H2804, at a-rate of flow of 98 parts byweight in a given time and 34 parts by weight of gaseous ammonia admixedwith air in volume ratios of 1 to 9 are contacted at 125 C. followingthe same procedure as described in the example given for the manufactureof mono-ammonium phosphate.

The three examples presented are illustrative of means for themanufacture of numerous materials, by the use of the described processand apparatus, by combining a reactive gas and a reactive liquid of highconcentration to form a solid reaction product of good quality.

The selection of the temperature for the re-' action zone and itsuniform maintenance are matters of first importance. The temperatureselected may be one in a considerable range of values for satisfactoryoperation and for this reason some indication of its influence uponother factors is included. An increase in temperature of the reactionzone will permit the use of a higher partial pressure of reactive gas inthe inert gas mixture and at the same time will require a decrease inconcentration for in order that the predetermined temperature may bemaintained.

Certain terms used throughout the description and claims are understoodto have the following meaning: reactive gas refers to the reagent whichis gaseous under normal standard conditions or, being liquid under thoseconditions, exists in the gaseous phase when mixed with the inert gas asrequired for the operation of this process; concentrated acid orconcentrated reactive liquid refers to strongbut not necessarilyanhydrous material, since the process is sufiiciently'fiexible tooperate within reasonable limits and still obtain I a solid finalproduct of good qinlity; and inert gas refers to any gas or mixture ofgases which does not exert any appreciable chemical reac-g tivity whenbrought in contact with any of the raw materials or with any of theintermediate or finished products.

I claim: I a

1. Process of making an ammonium salt of a mineral acid, whichcomprises, mixing gaseous ammonia and an inert gas in such proportionsthat the partial pressure of the ammonia in phate, which comprises,

the reactive liquid the gaseous mixture is greater than the vaporpressure of ammonia above the ammonium salt, and less than the vaporpressure 01' ammonia over the next compound in theseries containing alargerproportion of they ammonia in combination where more than onecompound may be made from the ammonia and the mineral acid,

.at the temperature of the reaction zone. with the amount of. theammonia in the gaseous mixture being at least that required to form theammonium salt, and contacting the gaseous mixture continuously'andcountercurrently with 1 a'sprayof the mineral acid, with the time orcontact of the reactants being' suiilcient to result in asubstantialequilibrium between the reactants at the elevation of thepoint of admission of the gaseous mixture.

2. Process of making di-ammonium phosmixing gaseous ammonia and an inertgas in such proportions that the partial pressure of the ammonia in thegaseous mixture is greater than the vapor pressure of ammonia abovedi-ammonium phosphate and less than the vapor pressure of ammoniaabovetri-ammonium phosphate at the temperature of the reaction zone,with the amount of the ammonia in the gaseous mixture being at leastthat required to form the di-ammonium phosphate, and contacting thegaseous mixture continuously and countercurrently with a spray ofphosphoric acid, with the time of contact of the reactants beingsufllcient to result in,a substantialequilibrium between the reactantsat the eieva tion of the point of admission of the gaseous mixture.

3. Process of making mono-ammonium phosphate which comprises mixinggaseous ammonia and an inert gas in such proportions that the partialpressure of the ammonia in the gaseous mixture is greater than the vaporpressure of ammonia above mono-ammonium phosphate and less than thevapor pressure of ammonia above di-ammonium phosphate at the temperatureof the reaction zone. with the amount of the ammonia in the gaseousmixture being at least that required to form the mono-ammoniumphosphate, and contacting the gaseous mixture contlnuously andcountercurrently with a spray of phosphoric acid, with the time ofcontact of the reactants being stantial equilibrium between thereactants at the elevation of the point of admission of the gaseousmixture.

4. Process of making mono-ammonium sulfate, which comprises, mixinggaseous ammonia and an inert gas in such proportions that the partialpressure of the ammonia in the gaseous mixture is greater than the vaporpressure of ammonia above mono-ammonium sulfate and tants beingsuflicient to result in a substantialequilibrium between the reactantsat the elevation of the point of admission of the gaseous mixture.

HARRY A. CUR'I'IS.

sufii'cient to result in. a subthe temperature of the

